And other news from science and technology.

(For the latest Human Nature columns on anal sex, fetal pain, and animal rights, click here.)

Researchers put a human chromosome in mice. The idea is to study causes and treatments of Down's syndrome, which is caused by an extra copy of this chromosome. The chromosome was fused into mouse stem cells, which were then reinserted in mouse embryos, which in turn were implanted in their mothers and brought to term.

People who need organs are using the Internet to recruit donors. They're using Web sites (HelpMyGrandpa.com, MichaelNeedsALiver.com), chat rooms, and e-mail to circumvent the nonprofit organization that allocates organs from cadavers. Supporters say it's efficient; critics say it will help rich and clever people get all the organs.

Scientists are trying to find genetic causes of bulimia and anorexia. They think this is possible because the disorders run in families. The research involves looking for genetic patterns in patients who have "core" traits such as perfectionism, anxiety, and preoccupation with mistakes.

One of every three American women aged 22 to 24 claims to have had anal sex. (For Human Nature's take, click here.)

Chevron and a California town will try to fuel a sewage plant with cooking grease from nearby restaurants. The idea is to cut energy costs and ease the burden on landfills.

Mars is experiencing global warming. Its southern polar cap is shrinking at a rate of 10 feet per Martian year. Scientists don't know why, but industrial pollution can be ruled out.

American spending on medical research has doubled. More than half the roughly $100 billion we spend annually comes from the private sector; a quarter comes from government. Pessimists say all this money isn't curing diseases fast enough. Optimists say we've forgotten the diseases we've cured.

NASA will spend more than $100 billion to return to the moon. The plan has three stages: earth orbit, then moon orbit, then descent to the moon. The idea is to set up permanent moon bases to develop technologies for missions to Mars and beyond.

Human fetal stem cells restored mobility in mice with spinal cord damage. The cells were taken from 16- to 18-week aborted fetuses. (For Human Nature's take on harvesting fetal tissue, click here.)